1. Field of the Invention
The present invention relates to a fabrication apparatus for an automotive fuel tank which is made from a thermoplastic synthetic resin and more particularly to a fabrication apparatus for an automotive fuel tank whose outer wall is formed from a thermoplastic synthetic resin through blow molding and which has a built-in part in an interior thereof
2. Related Art
Conventionally, metallic fuel tanks were used as fuel tanks for motor vehicles and the like. In recent years, however, fuel tanks made from thermoplastic synthetic resins have been in use due to thermoplastic resin materials being light in weight to satisfy increasing demands for vehicles which are light in weight, being free from rust, being easy to be molded into desired shapes.
A blow molding approach has been used in many cases in fabricating automotive fuel tanks from thermoplastic resins because the blow molding approach facilitates the molding of hollow objects. In the blow molding approach, a parison made of a molten thermoplastic synthetic resin member is extruded into a cylindrical shape from above, and air is blown into the parison while the parison is being held by molds to thereby fabricate an automotive fuel tank.
On the other hand, also in the blow molding approach, it is required to provide built-in parts such as valves and baffle plates for suppressing flowing or lapping noise of fuel in an interior of a fuel tank.
Then, to make this happen, there has been proposed an approach in which a built-in part 120 is set in a resin frame, and the resin frame is set within a mold, so that the built-in part 120 is made to be secured to an inner circumferential surface of an outer wall of a fuel tank through blow molding, whereby the built-in part 120 is mounted in an interior of the fuel tank (for example, refer to JP-A-1-301227).
In this case, however, since the built-in part 120 is set in the resin frame and is then secured to the inner circumferential surface of the outer wall of the fuel tank, labor hours have to be involved in cutting to remove the resin frame after the fuel tank has been molded, and with a small built-in part 120, a large resin frame has to be used, often resulting in a case where the weight of the molded fuel tank is increased.
Then, to cope with this, a fabrication apparatus as is shown in FIGS. 11 to 12 is used in placing a built-in part in an interior of a fuel tank (for example, refer to JP-A-6-143396 and U.S. Pat. No. 5,326,514).
In this apparatus, firstly, as is shown in FIG. 11, a built-in part 220 is placed on a holding rod 241 of a built-in part holding unit before a parison 208 is set in a blow mold 240, and then, the blow mold 240 is opened to position the built-in part 220 in an interior of the blow mold 240. Thereafter, with the blow mold 240 left open, the parison 208 is lowered, so as to position the built-in part 220 in an interior of the parison 208.
As is shown in FIG. 12, thereafter, press pins 242 are made to project inwards from both sides of the blow mold 240 before the blow mold 240 is closed to press against the parison 208, so as to press the parison 208 to side ends of the built-in part 220. As this occurs, since an inner surface of the parison 208 has not yet been set then, the parison 208 and the side ends of the built-in part 220 can be fused together.
Then, the holding rod 241 of the built-in part holding unit is lowered, the blow mold 240 is closed, and air is blown into the parison 208 for blow molding.
In this fabrication apparatus, since the construction of the built-in part 220 is simple, the built-in part 220 is simply placed on the holding rod 241. However, in the event that a built-in part has a complex shape as with a built-in part 220 of a fuel tank, the built-in part 220 has to be held in a predetermined position in an ensured fashion. In addition, with a soft built-in part 220, there has been a situation in which part of the built-in part 220 hangs due to its own weight.